The invention relates to a data recording apparatus and a shut-down method for a data recording apparatus, and more particularly, to a technique for shutting down an apparatus for recording control parameters in a control unit mounted in a vehicle.
Conventionally, a data recording apparatus, for loading and recording control parameters of a control unit mounted in a vehicle in order to identify a faulty condition of the vehicle, is known. For example, JP-A-2002-070637 discloses a data recording apparatus which effectively utilizes a limited storage capacity to reliably and efficiently record data for a control unit. This data recording apparatus chronologically samples a variety of data (i.e., control parameters) in the control unit of a vehicle. Then, a sequence of sampling data is stored in a data recording section upon establishment of a predetermined trigger condition which corresponds to a condition under which effective data can be acquired for identifying a faulty condition of the vehicle. The data recording apparatus continues to executes such a recording operation over operation cycles of the vehicle, and switches to a sleep mode in four minutes after an ignition switch is turned off for power saving.
However, if the data recording apparatus switches to the sleep mode in a predetermined time after the ignition switch of the vehicle is turned off, it is difficult to achieve the compatibility between an improvement in the reliability of recorded data and a reduction of power consumption in a battery. This is because a situation takes place where a timing at which the data recording apparatus switches to the sleep mode is different from a timing at which the controller terminates the operation. Each controller contained in a vehicle terminates its operation at a timing which is set on an individual basis. Thus, when a controller terminates the operation before the data recording apparatus switches to the sleep mode, the power stored in the battery will be consumed for nothing. On the other hand, when the data recording apparatus switches to the sleep mode even though a controller is still operating, a situation takes place where the data recording apparatus terminates a recording operation even though data should be still recorded.